In recent years, many portable electronic devices such as a combination camera (Videotape Recorder), a mobile phone, and a notebook personal computer have been introduced, and downsizing and weight saving of such devices have been made. Research and development for improving the energy density of the battery used as a portable power source for such electronic devices, in particular the secondary battery as a key device has been actively promoted. Specially, a nonaqueous electrolyte secondary battery (for example, lithium ion secondary battery) provides the higher energy density compared to a lead battery or a nickel cadmium battery that is a conventional aqueous electrolytic solution secondary battery. Therefore, improvement thereof has been considered in respective fields.
Lithium ion secondary batteries with various shapes have been developed. As one thereof, there is a lithium ion secondary battery in which a cathode and an anode are layered and spirally wound with a separator in between, and a center pin is inserted in the center of the spirally wound electrode body. The existing center pin has, for example, as shown in FIG. 34, a cut line 131 in the axis direction of a tubular main body. When an external force is applied to the battery, a main body 130 is flattened out. In the result, the edge of the cut line 131 is opened outward, and the opened portion penetrates the separator, and short-cuts the cathode and the anode. Thereby, battery reaction is blocked, and power generation function is safely deprived.
There is an existing battery in which, for example, a plurality of grooves are provided for the center pin in parallel to the cut line, or a battery in which the edge of the cut line is wave-shaped, so that short-circuit between the electrodes is generated regardless of directions of the applied force (for example, refer to Patent document 1). Further, it is proposed that short-circuit is easily generated extensively by spirally providing a concave portion on the surface of the center pin, or by forming the center pin of a coil spring (for example, refer to Patent document 2 and Patent document 3).    Patent document 1: Japanese Unexamined Patent Application Publication No. 8-255631    Patent document 2: Japanese Patent No. 3178586    Patent document 3: Japanese Unexamined Patent Application Publication No. 8-273697